Argan oil can replace up to 67% of fish oil in juvenile rainbow trout diets without affecting growth performance or feed efficiency, according to a study published in Aquaculture International titled Dietary argan oil for juvenile rainbow trout: growth performance, fatty acid profile, and antioxidant defense.
Researchers tested diets containing 0%, 33%, 67% and 100% argan oil replacement during an eight-week feeding trial involving rainbow trout weighing approximately 2.6 grams. Fish in all groups reached around 15 grams by the end of the study, with no significant differences in growth, feed conversion ratio or survival.
The study found that levels of the omega-3 fatty acids EPA and DHA declined as argan oil inclusion increased. However, trout fed the 67% replacement diet maintained EPA and DHA levels that the authors considered comparable to the control group.
Researchers also reported improved antioxidant status in fish receiving higher levels of argan oil, with lower markers of lipid oxidation and higher levels of reduced glutathione. The authors attributed the effect to the oil’s high content of unsaturated fatty acids and antioxidant compounds.
While the study concluded that fish oil could be fully replaced under the conditions tested, the authors suggested 67% replacement as the most practical long-term option because it preserved omega-3 retention while providing antioxidant benefits. They noted that residual fish oil supplied through fishmeal may have contributed to performance in the 100% replacement group.